The Cure
by gabrielstolethetardis
Summary: Dean's incurable, as it happens—turns out a Knight of Hell can't be cured by a simple blood spell—so Sam entrusts him to Cas, who tries desperately to ignore Dean's sarcastic remarks and constant instigation.


"What do you mean, it's not working?" Sam demands, his eyes wide and slightly frantic. "It worked with Crowley!"

Cas glances behind him, where Dean sits bound to an iron chair within a hastily painted devil's trap, his head hanging limply. "It appears that Knights of Hell cannot be cured using the same blood ritual you used in your attempt to turn Crowley human. I suspect it has something to do with the Mark of Cain and the hold that it has on Dean."

Sam flounders for a moment before spitting out, "Well, we'll try something else, then. Maybe he needs something stronger than human blood. Angel blood? Grace? Something has to work."

"Angelic substances would kill him," Cas says. "His soul is too corrupt."

"Well then what, Cas?" Sam exclaims, frustration evident in the hard line above his eyes. "We can't just leave him like this!"

"Oh, come on, Sam," Dean calls, accenting his words with a laugh, and Cas and Sam both swivel to see Dean upright in his chair, eyes dancing with amusement. Then, they flush black, tinting the amusement with something much darker, and Cas suppresses a shudder. "You can't do anything! Your little _cure_ is useless. You may as well just let me out of here." He rattles the chains binding him encouragingly, and when he blinks, the green's back—but the demonic mirth still remains, tinting Dean's face in a way Cas never thought he would see.

Sam grabs Cas' shoulder, fixing him with an intense stare. "Like _hell_ we can let him out of there," he hisses. "He's not my brother—not anymore."

Cas lowers his gaze to the floor. "I know." He's only studied the demon's face hundreds of times, trying to find Dean within it and failing.

Sam bites his lip, glancing over at Dean; Dean gives him a head nod and a toothy grin, which makes Sam's jaw twitch like it does when he's trying to hold in a bout of violent emotion. "I'll keep looking," he decides, letting go of Cas' shoulder and straightening, shaking his shoulders a little as if to release the tension that has a firm hold on his entire body. "You stay here and watch him. Keep giving him the syringes of blood—maybe we just haven't injected him with enough yet."

"Sam—"

"Please, Cas." Sam gives Cas a pleading glance. "I have to keep trying. I need to get my brother back."

Cas pauses, then nods, taking a step back from Sam. "Work as quickly as you can. The longer Dean remains a demon, the harder it will be to reverse the effect of the Mark."

Sam murmurs his agreement before retreating into the main part of the bunker, swinging the door shut behind him and sealing Cas in the room with Dean, who at the moment is humming Metallica and drumming his fingers on the arm of the chair in time with the beat. As soon as the door shuts, however, he stops drumming and says, "Sammy put you on babysitting duty?" He lets out a breathy laugh, shaking his head. "He must not trust you one bit."

"He trusts me enough to know that I won't let you out." Everything in Cas hates seeing Dean in chains—but then he looks at Dean, sees the demon's grinning face, and tells himself that it's not Dean, not really.

"No?" Dean cocks an eyebrow and sighs. "Well, it doesn't really matter. We can pass the time, right? Let's talk, Cas."

"About what?" Cas' tone is hard, almost bitter, as he steps into the room containing Dean and closes the hidden door behind him, sealing himself in. "We have nothing to talk about."

"Ah, come on," Dean says, his eyes twinkling with amusement. "Nothing? After all we've been through?"

" _We_ ," Cas says through grit teeth, "haven't been through _anything_."

Dean laughs, short and clipped, and locks eyes with Cas; despite the ugly face underneath, Dean's eyes remain, a deep green that makes Cas' stomach twist with a surge of emotions. "You and Sammy are trying _so_ hard to convince yourselves that I'm different—that I'm not Dean anymore—but you're wrong and you know it, Cas. I'm the same guy you pulled from Hell all those years ago, the same guy you rebelled for, the same guy who stopped the Apocalypse." His eyes flush black then, and he shrugs as if it's no big deal. "Well, I guess I'm not human anymore, but hey—neither are you."

"No," Cas says, feeling frustration building within him, red-hot and volatile. "You're not _Dean_ anymore. Dean is dead."

Dean quirks an eyebrow. "No? Are you sure?" The black bleeds out of his eyes slowly, leaving glass-bottle green in its wake, and slowly Dean's face softens, the hard edges making way for gentle lines and curving slopes. His shoulders loosen, his fingers flattening on the edges of the chair's arms, and a long, rattling sigh rips its way out of his lips, one that makes something inside of Cas throb.

Then, Dean meets Cas' eyes, and suddenly it's _gone_ —the evil, the ugliness, the hellfire that threatened to consume Dean from the inside out. Dean sucks in a shaky breath, looking at Cas like he's the only thing left that matters; his lips form Cas' name, breathing it out softly, and Cas can't take it anymore.

"Dean," he gasps, and he doesn't care that it's all too convenient—that it could be a trick, that the demon's probably still lurking in Dean's subconscious, that this Dean—despite appearances, internal and external—could still possibly be infected. His frustration and accumulating rage seeps away, leaving plenty of room for the swell of positive emotions that flood his system and drive him forward until he's standing inches from Dean. "This…" He tries to shake the relief controlling him, to think logically. "This can't be you."

He turns his back to Dean, taking a step away, but Dean stops him with a quick, "Cas, wait."

Cas doesn't turn, waits for Dean to continue. When Dean speaks again, his voice is hoarse, and Cas can't help but wonder if this is real. "I know what I am. I know what I did, and I know what you and Sam are trying to do."

Cas glances over at the array of hypodermic needles, spread out across the table; over half of them are empty, already running through Dean's veins. "It's not working," he mutters, moving to stand in front of the table and palming a needle, turning it over and over in his hands absently. "You're still…" He can't say it.

"You have to kill me."

Cas turns then, the needle still grasped in his hand, to see Dean slumped in his chair, his forehead tight and his fingers gripping the armrest tightly. "What?"

"You have to kill me, Cas!" Dean growls, his words strained. "I can't- he wants control again."

"I can't kill you, Dean." Killing Dean… the thought makes Cas sick to his stomach.

"Goddammit, Cas!" Dean exclaims, his eyes flashing black briefly before snapping back to green. "Just… do… it! Please, I'm begging—"

Dean's words cut off abruptly, and there's a moment of stillness before a slow smile creeps over Dean's lips. Then, Dean looks up, his eyes a deep black, and says, "That's enough of that. God, I let him have control for _one minute_ and he thinks he can just run the show." He clicks his tongue against the roof of his mouth and shakes his head. "How rude."

Cas feels like he's just been dragged through a meat grinder and spat out the other side a crushed, pulpy mess. Instead of responding, he jabs the needle in his hand into the side of Dean's neck and releases Sam's blood into Dean's arteries, hating the shudder that goes through Dean at the injection. "You could be gentler," Dean groans as Cas slips the needle back out of Dean's neck and tosses it back onto the table. "I can still bruise."

Cas bites his lip and takes a step backward. "Why did you do that?"

Dean's eyes gradually fade back to green as the human blood takes effect, but they lose none of their mirth. "Oh, come on, Castiel," he teases, and Cas almost flinches at the use of his full name. If he needed any more proof that the thing sitting in front of him isn't Dean, that was it. "Why not? You may be an angel, but your little stunts with humanity have given you feelings, and they're just so _fun_ to toy with." He leans forward, as far as he can go with the iron chains taught against his chest, and simpers at Cas. "Let's play a game, Cas."

Cas' jaw twitches, but he remains quiet as Dean continues, "I'll keep talking, and we'll see how long it takes you to break." His voice drops mockingly. " _You have to kill me, Cas._ Please. You don't have the guts."

Cas digs his fingernails into his palm, feeling no pain but using the tight sensation to control the anger rising within him.

Dean leans back in his chair. "No? Okay, let's try something else. Let's talk about _why_."

Cas says nothing.

"Why can't you take that knife and just run it through my heart?" Dean muses, nodding toward the demon knife sitting idly to the left of the needles—for worst-case scenarios, though Cas knows he could never use it. "You know there's no other option. Human Dean, he wants you to—hell, he was _begging_ you to kill him. We both know that I don't beg for much."

 _Stop_ , Cas wants to say. Instead, he turns and mindlessly organizes the contents of the table, straightening syringes and throwing empty ones into a paper bag on the floor.

"But you, heaven's warrior, refuse to kill a demon," Dean muses. "Now why could that be? You've killed a lot more for a lot less."

Cas runs out of things to straighten, so he simply takes a syringe in his hands and studies it, trying to determine why the blood isn't working on Dean, though he knows that his efforts are futile.

"Ah, I know," Dean says, and Cas can hear his smirk in the tone of his voice. "It's because you love me."

The syringe cracks under the sudden pressure of Cas' fingers, spattering blood all over the table and coating Cas' hand with vibrant red. He lets out a shaky breath, closing his eyes and placing his hands flat on the table to brace himself.

"And we have a winner!" Dean crows. "I bet the thought of killing me makes you all twisted up inside. Just imagine: the moment that blade sinks into my chest, I'll give the other Dean control, just so you can see the betrayal and pain in his eyes before the light goes out. Maybe he'd even try to say your name, but he couldn't around the blood bubbling up in his throat. You'd probably be able to hear the final beats of his heart as it struggles to keep beating. But the best part?"

Cas turns, finally, the edges of his vision red, to see Dean's eyes flash black. "In that final moment, I'd come back, just so I could drive that pretty little angel blade in between your rib cage."

"Stop," Cas growls, grabbing Dean's throat with one hand and pushing until the chair stands on two legs, the only thing keeping it up being Cas' grip on Dean's neck. "You're wrong."

Dean manages to laugh around Cas' tight grip on his windpipe, his Adam's apple bobbing against Cas' palm. "Then why are you so angry?"

Cas reaches instinctively for Dean's forehead, barely stopping himself from laying his palm on Dean's skin and burning until there's nothing left of the evil inside. His hand hovers centimeters from Dean's hairline, and then he drops both hands and steps back as the chair rocks back onto all fours, clattering noisily on the stone floor—not loud enough to cover Dean's laughter, though.

"He loves you too, you know," Dean says after he's finished, his raucous grin fading into a small smirk. "Technically, we both do. I just don't care."

Cas turns so Dean can't see the look on his face and busies himself cleaning the spilt blood from the table using the sleeve of his trench coat. The red blossoms against the tan fabric, spreading like an artist's paint strokes and fading gradually to a dull rust color. He lets the methodical cleaning distract his mind from the words Dean has uttered, trying not to think about the fluttering in his chest.

"How does that make you _feel_ , Cas?" Dean goads, rattling his chains. Then, like a chant: "Dean loves Cas, Cas loves Dean. Dean kills Cas, Cas kills Dean. Very poetic."

Tightly, Cas says, "You know nothing."

"I know everything," Dean counters, his voice losing some of its lightness. "I know how terrified I was when I first saw you, but also a little bit amazed. I know how much it hurt every time you betrayed me, even though I held out hope that you would bounce back. I would have accepted any apology, even if I pretended otherwise. I know how dead I was inside after you walked into that lake with the Leviathan and didn't walk out and how, when I found out that you were alive, I wanted nothing more than to take you in and protect you from the horrors that were your past. I know that there's no exact moment when I fell in love with you—I just woke up one day and realized that that's what it had been the whole time and I was too stupid to see it."

Cas had turned to face Dean halfway through his speech, and as Dean spoke, it was so easy to convince himself that this is really Dean talking, that he means every word. However, that illusion shatters when Dean's lips curl upwards, his eyes lighting up with something cruel, and he says, "And now I know that I could stab you and I wouldn't feel an inch of regret."

Cas sucks in an involuntary breath and says, "You're lying."

That brings Dean up short. He quickly recovers, however, and says, "Sometimes, Cas, it's more to my advantage to tell the truth. After all, why lie when there's all of _this_ just waiting to come to light?"

Cas shakes his head. "Not an inch?" he says, taking a step toward Dean. "You say you don't care, and maybe you don't, but someone who remembers feelings that vividly can't just shut that off—not even a demon."

Dean clicks his tongue at Cas. "Now who's lying? Honey, I could gut you right here and my only concern would be the mess."

Cas twitches at the pet name, clenching his fists slightly to relieve some of his tension. Then, even though he knows it's too soon—he still has a good 45 minutes before Dean's due for his next injection—Cas turns, grabs a syringe, and plunges it into the side of Dean's neck, trying to ignore Dean's surprised exhalation as he presses the plunger down swiftly. "Guess I pissed you off," Dean gasps as Cas withdraws the needle and tosses it behind him, hearing it shatter against the wall and the small glass fragments rain down on the stone floor.

"Shut up," Cas growls, whipping around and approaching the table again. "I don't want to talk anymore."

"Fine." Dean's chains rattle and snap, and suddenly Cas finds himself thrown up against the wall with Dean standing inches away, his breath tickling Cas' lips. "I'll just kill you instead."

Cas' throat is tight under the pressure of the invisible hand holding him tightly to the wall, but he manages a strangled, "How?"

Dean laughs, slipping his hand inside Cas' trench coat and withdrawing a silvery angel blade. It glints in the dull light, and Dean regards it with admiration, turning it in one hand and using the other to grab a fistful of Cas' trench coat. "I guess your little spell gave me just enough humanity to slip out of that devil's trap." He flicks the hand with the knife at Cas, and the hold on him tightens, stealing his breath away. "Not enough to cure me, of course." Then, the knife presses up against Cas' chest, the tip just barely piercing his skin, and a blue glow begins to filter into the room. Dean's eyes flush black, his grin deepening, but Cas can tell that he's weak; though the hold on his body remains strong, Cas has enough power to raise his arm, to push Dean's hand away, and use a fraction of his own grace to thrust Dean backwards, hard enough that he knocks into the opposite wall.

The hold on Cas' body loosens completely and Cas crumples, catching himself at the last second and keeping himself from falling to the floor. He glances up at Dean, blue light still spilling from his chest, and straightens, watching Dean struggle to his feet and wipe a small trickle of blood from the corner of his mouth. "You don't want to fight me," Dean chuckles, spreading his arms wide. "You won't hurt me."

"You are correct. I don't want to fight you." Cas knows Sam had to have heard them tossing each other around; he just needs to stall Dean until Sam gets down here. "However, it appears that it may be necessary." Cas doesn't have an extra angel blade, but the knife is still on the table; however, Cas doesn't make a move for it. Even if he could pin Dean down, he wouldn't kill him—he _couldn't_ kill him.

Dean moves swiftly until he stands close enough to Cas that driving the angel blade through his heart would be no problem. "You really are a spineless son of a bitch," he says, the blade hanging casually at his side. Then, before Cas can react, Dean steps forward and presses his lips to Cas', using his free hand to take a fistful of Cas' trench coat.

Shock jolts Cas' system so violently he almost pulls away, but the wave of pleasure that shortly follows is enough to keep him where he is, Dean's lips warm on his and _gentle_ , and Dean's eyes are green.

They're green, and the lines are soft, and when Dean breathes Cas' name against his lips, Cas crumbles into him, closing his eyes and letting himself fall into the sea of relief and bliss and tranquility that Dean's kiss brings. He's not sure where to put his hands at first, so they just end up on the back of Dean's head, his fingers carding through the fine hairs near the soft skin of Dean's neck, and even though something inside of him screams that it's too perfect, that Dean's too human, he can't stop melting into Dean.

That is, until the pain, white-hot and piercing, beginning in his stomach and spiraling out to encompass his entire body. He breaks away from Dean with a gasp, his eyes flying open, and everything registers in slow motion:

The blinding blue light, filling the room and bouncing off the walls.

The silver blade protruding from his lower torso, Dean's hand gripping the handle.

Sam's voice, shouting over the buzz in Cas' ears.

Dean's mouth, curled in a smirk, and his eyes, pitch black.

Cas lifts a hand, feeling even that motion send spikes of pain through his entire being, and covers Dean's eyes. Then, his head tilts back and he collapses against Dean, his grace exploding in a blinding flash of white-hot light, and everything goes dark.

Sam watches in horror as Cas collapses against Dean, the light of his grace encompassing them both in a supernova of power, and too suddenly it's over, leaving Cas' body slumped against Dean. After a stunned moment, Cas just drops to the ground, his face slack, and Sam breaks from his trance, running to Cas and dropping to his knees next to him. "Cas?" he exclaims, like it's going to somehow bring the angel back.

He gets only silence in response.

Then, Sam hears a loud clatter, and he glances up to see Dean's face go white, the black in his eyes completely gone. Sam stands quickly, staring at Dean and _waiting_ , but then Dean lets out a strangled sob and takes a step back from Cas, bringing a white-knuckled fist to his lips. "I did this," he manages, his voice hoarse, and Sam knows it's _Dean_ —the way he stares wide-eyed at Cas, consternation quickly making way for piercing grief and debilitating self-hatred. "I remember everything."

He rubs his arms and then winces. He and Sam glance down at the same time to see the dark black imprint of… _something_ , seared onto Dean's skin. Onto every last inch of it.

Dean has his shirt off in seconds, staring down at his chest in blurry-eyed confusion that transitions quickly into raw horror.

Wrapping around Dean's entire body are the burnt remains of Cas' wings, permanently etched into Dean's skin. Feathers, bone structure, the tiniest details—they're all visible, and Sam doesn't have to look to know that they're _everywhere,_ save Dean's face. Even years from now, when Dean's had time to recover, the burns still catch him off guard occasionally. Sam sometimes jolts awake to the sound of knives that don't need to be sharpened grinding against the whetstone or the methodical clicking of guns being taken apart and put back together without a thought, but he says nothing.

Eventually, it's a vampire that does him in. It's just a run-of-the-mill job, but Dean and Sam are tired—they've been tired since day one, Sam figures. It's a wonder they even lasted this long. When Sam bursts into the vampires' nest, his machete covered in blood from a rough struggle outside, he meets the equally as bloody fangs of a young female vampire, and that's it. Lights out.

Dean, the last one standing. Who would've thought? He spends the good part of a year tracking down any vampires he can find and decapitating them, but eventually he runs out of leads and energy and decides to go to Jody—whether to work with her or say goodbye, he hasn't decided.

He never gets the chance.

Like a captain going down with his ship, Dean dies in the Impala, slammed from the left by a semi in a blind intersection. He barely registers the headlights before they collide, and then his neck snaps on impact.

And there's Cas, waiting for him in heaven and saying something about 'soulmates' and 'shared heaven,' and Dean can't help but kiss him.


End file.
